Currently, paper shredders may incorporate a variety of thickness detectors which can be expensive, complicated, and prone to failure. Thickness may be measured with a pivoting member extending into the throat of the shredder. When paper is inserted into the shredder, it may contact the pivoting member and force the pivoting member to rotate about its axis. In turn, the opposite end of the pivoting member, which is placed outside of the throat and generally in the upper cover of the shredder, may move upwardly. That end of the pivoting member may be in communication with a sensing device which measures the degree of rotation of the pivoting member to approximate the thickness of the paper. When the measuring device determines that the pivoting member's rotation has exceeded a predetermined threshold corresponding to a predetermined maximum thickness of the paper, circuitry coupled to the measuring device may direct the shredder to perform an operation such as shutting the shredder off so that the shredder's motor is not damaged by the overly-thick paper.
In application, the thickness detector's measurement of paper thickness may vary as the paper is shredded due to many factors such as the cutting blades shaking the paper back and forth as the paper is shredded. This shaking, often referred to as fluttering, may cause the thickness detector to rotate excessively and incorrectly signal that the thickness of the paper has exceeded the predetermined maximum thickness when the actual thickness of the paper may be within the shredder's capacity range. As such, the paper shredder may prematurely shut-off, even though the actual thickness of the paper has not exceeded the shredder's capacity.
Control circuitry utilizing algorithms has been developed in an attempt to correct for the inaccurate thickness measurement caused by paper shaking. Also, fixed counterweights have been incorporated into the thickness detecting assembly to dampen the movement of the pivoting member. In some instances, the fluttering of the paper may be measured by the thickness detector and, in connection with specially programmed circuitry; the predetermined maximum thickness threshold may be temporarily raised to account for the false readings caused by the paper shaking back and forth.
Also, thickness detecting systems may just notify users that the maximum thickness capacity of the paper shredder has been exceeded, but do nothing more than prevent the paper shredder from operating until the paper is removed from the feed opening.
What is needed is a reliable and cost-effective solution for accurately measuring the thickness of material inserted into a paper shredder prior to and during the operation of the shredder's motor, as well as for assisting users to safely remove the paper from the throat.